Recently, low tire pressure has become an issue in the news because many travelers have died from rollover accidents due to low tire pressure. Automakers have determined that it would be a safety initiative to have a dash read-out that would tell the driver of a vehicle when they have low tire pressure. Therefore, a new industry is coming forward to meet the demand of providing low pressure tire sensors to the automakers. In fact, in a white paper by Goodyear Tire & Rubber Company, and as published by the Society of Automotive Engineers, 250,000 accidents a year are a result of under-inflated tires. The cost in repairs due to accidents pales in comparison to the toll in human suffering due to injuries and even deaths that could possibly have been avoided had the driver been alerted of a potential tire problem.
Apart from the need to reduce the number of accidents and resulting injuries, there are major ecological implications for this technology. For instance, if a tire is under inflated by just 5 psi, it increases fuel consumption by 10%. Simplistically, in England alone, some 200,000 gallons of fuel per day could be conserved with proper tire pressure. This equals 73 million gallons per annum, a savings into the millions of dollars with considerable environmental benefits.
Many vehicles have had one or more tires deflate or go completely flat, sometimes even violently as in the case of a blowout while traveling. At times the driver is not immediately aware of the situation and may continue to drive on the remaining tires, dragging them on the pavement and causing them to become damaged as well. A blowout at high speeds can cause extensive damage if it goes undetected. The tire disintegrates and debris can damage the vehicle or other vehicles driving on the remnants of the now fragmented tire, steel belt, and bead wire. In the case of dual rear tires on a four-wheel axle, the size and subsequent louder noise and vibration experienced by the driver may cause this condition to go unnoticed, even resulting in the tire or even the vehicle catching fire.
Another concern about loss of tire pressure or low tire pressure is that it affects the load carrying capability, along with steering and breaking, affecting the overall control of the vehicle. This and the often disproportioned weight or center of gravity has lead to numerous roll-over accidents, resulting in an extensive loss of life, innumerable injuries, and devastating economic consequences for the drivers, passengers, insurance companies, vehicle manufacturers, and tire manufactures alike.
In an attempt to help to prevent further accidents of this nature, on Nov. 1, 2000, the United States Congress and former President Clinton passed and signed into law House Bill H.R. 5154 entitled the Transportation Recall Enhancement, Accountability, and Documentation (“TREAD”) Act. Section 13 of this new law requires that within three years of the final rule making proceedings, every passenger car, multipurpose passenger vehicle, and truck with a gross vehicle weight rating of 10,000 pounds or less will be required to have a warning system installed in the vehicle to indicate to the operator when a tire is significantly under inflated. It is expected that other countries will follow suit.
Many inventors have been working on this problem long before legislation mandated an attempted solution. Various electronic devises are found in the art including several examples of tire pressure monitors and alarm systems. These are typically fastened to the rim of the wheel and required that a hole be drilled through the wheel, or a monitor device be strapped or banded to a wheel in order to detect changes in tire pressure or temperature and relay the information to a receiving devise that then alerts the driver.
Sensors based on Surface Acoustic Wave (SAW) technology have been preferred by the original equipment manufactures (OEM) due to the affordability and availability of materials that can be utilized to create a substrate that has the appropriate properties for sending mechanical, or acoustic waves as the sensing mechanism. These sensors utilize piezoelectric material to generate the acoustic wave by generating an oscillating electric field thereby creating a mechanical wave, which propagates through the substrate, and then is converted back to an electric field by way of a signal for measurement. The devise needs no batteries, thereby avoiding any disposal problems or battery failure during operations. SAW devises are highly sensitive, very economical, and very tiny. Many manufacturers of this type of sensor prefer the placement of the sensor itself behind the air valve of a tire, using the brass stem as an antenna for transmitting the signal.
In the prior art, there are several examples of tire pressure monitors and alarm systems. These are typically fastened to the rim of the wheel and require that a hole be drilled through the wheel or attached through some sort of banding. See U.S. Pat. No. 4,954,677 or Alberter, et al.; U.S. Pat. No. 4,894,639 of Schmierer; U.S. Pat. No. 4,866,982 of Gault; U.S. Pat. No. 4,768,375 of Echardt, et al.; U.S. Pat. No. 6,378,360 of Bartels; U.S. Pat. No. 6,278,361 of Magiawala; U.S. Pat. No. 5,717,135 of Fiorietta; and U.S. Pat. No. 4,784,993 of Lothar, et al. These systems include a transducer of some sort that converts the pressure to a signal for communicating the pressure to a remote display.
The disadvantage to this valve stem antenna design is that it requires some sort of modification of the wheel rim or valve stem, often requiring holes drilled in the wheel to receive the transducers, thereby causing undue stress on the wheel, retrofitting existing wheels, and raising legitimate safety concerns. Additionally, the attachments can vibrate loose causing sensitive instruments to fail transmitting their signal accurately to the monitor located in the cockpit of the vehicle.
The problem of connecting the transducer to a monitor has been solved in part by radio frequency communications. As shown in U.S. Pat. No. 4,890,090 of Ballyns, a pressure transducer is coupled to a radio frequency transmitter that is mounted within the tire and secured to the wheel rim. Although it has the advantage of wireless communication of the pressure to a remotely placed monitor, it suffers from the same disadvantages of the rim and valve stem mounted sensors in that they are difficult to install and may become easily damaged and thereby prove to be unreliable.
To avoid this communication problem, it is possible to indirectly monitor the condition of the tire using tire rotation sensors like those installed as original equipment on vehicles with anti-lock braking and some all-wheel drive systems. To detect a deflating tire, these sensors are monitored for abnormal changes in rotation speeds of the tire indicating deflation. Doing so requires sophisticated sensors, data processing equipment and algorithms, and a vehicle originally equipped with this advanced and expensive technology. Although it is a sophisticated approach, it is not feasible for most vehicles such as buses, trucks and motor homes currently being manufactured.
Despite previous substantial efforts to improve the safety of tires, current tire pressure monitoring systems continue to be expensive and elaborate; they require substantial modification to existing wheels and to the car for their use; and they offer methods having little to no feasibility for retrofitting the millions of ordinary wheels that are in use and will continue to be manufactured and used.
The current invention discloses several new approaches to monitoring tire pressure and temperature in tubeless tires. Either a new type of antenna may be used, or the entire package of the sensing device and the electronic circuitry, which includes the transmitter and an antenna, can be incorporated into a composite wheel rim during manufacturing. The sensor and subsequent electronics are in a sealed housing to protect the components from physical damage from flat tire lubricants, tire sealants, and the elements. The housing is embedded in the composite recessed rim portion of the wheel so as to be affected by the changes in pressure and temperature, without degrading the accuracy of the signal through the variations of vibration experienced by other sensor devises. The composite materials lend themselves well to conductivity and will in no way impede the RF signal sent by the SAW devise to the receiver.
A composite wheel is under development by several of the wheel manufacturers currently supplying original equipment to the automotive, truck, agricultural, utility, and RV markets. These wheels are stronger than conventional steel wheels, and much lighter. By significantly reducing the weight of the wheel, fuel economy is greatly enhanced. The lighter wheels are much easier to store, ship, mount, and manually handle than their steel counterparts. The cost of these composites is comparable as well with traditional steel wheels, but require less energy to produce.
The sensor devise itself may be one of many described herein and is not limited to the sensors listed, as this technology is rapidly developing and the most ideal sensing device has not yet been determined. Suitable sensors which may be incorporated herein by reference may include U.S. Pat. No. 4,954,677 of Alberter, et al.; U.S. Pat. No. 4,894,639 of Schmierer; U.S. Pat. No. 4,866,982 of Gault; U.S. Pat. No. 4,768,375 of Echardt, et al.; U.S. Pat. No. 6,378,360 of Bartels; U.S. Pat. No. 6,278,361 of Magiawala; U.S. Pat. No. 5,717,135 of Fiorietta; and U.S. Pat. No. 4,784,993 of Lothar, et al. Further disclosures that are also incorporated herein by reference are: European Pat. No. EP0518900 B1 of Lonsdale; U.S. Pat. No. 5,585,571 of Lonsdale; PCT/GB97/03028 of Lonsdale; British Pat. Nos. 9902341-8 of Perry; 9909652.1 of Transense; 9925873.3 of Transense; 99258736.3 of Transense; 9925538.2 of Lonsdale; GB9917579.6 of Transense; and 9915052.6 of Transense.
It would be advantageous if the antenna could also be embedded into the composite material of the wheel and wound around the hub of the wheel itself. A toroidal antenna, possibly helical in nature, may be permanently incorporated into the wheel during manufacturing. The preferred antenna is described in U.S. Pat. No. 5,734,353 of Van Voorhles, et al.; U.S. Pat. No. 5,442,369 of Van Voorhles, et al.; and U.S. Pat. No. 5,654,723 of Van Voorhles, et al., and is incorporated herein by reference as part of this work.
A particular benefit of this invention is that the sensor unit and circuitry embedded into the composite wheel, is not limited to tire sensors only. A vast array of sensing devises can be incorporated into the wheel that can communicate information about speed of the vehicle, footprint of the tire, accelerometers, breaking, steering, shock absorption, weight dispersion per axle or per tire, and considerably more information as can be relayed from tiny sensors that will interpret specific information into RF signals that will be translated into information transmitted to a monitor in the cockpit for the driver.